1. Field of Invention
The present invention pertains to the art of refrigerators and, more particularly, to a temperature control system for efficiently maintaining a substantially uniform temperature within a compartment of a refrigerator.
2. Discussion of Prior Art
In general, refrigerated appliances include a freezer compartment for maintaining foodstuffs at or below freezing, and a fresh food compartment, in fluid communication with the freezer compartment, for maintaining foodstuffs in a temperature zone below ambient temperature but above freezing temperatures. A typical refrigerator includes a refrigeration system including a compressor, a condenser, a condenser fan, an evaporator coil, and evaporator fan.
In operation, temperature sensors are arranged within the refrigerator to measure a temperature within a compartment. When a door associated with either compartment is opened, the temperature within the respective compartment will rise. When the internal temperature of the refrigerator deviates from a pre-selected temperature, the refrigeration system is caused to operate such that the temperature will return to a point below the selected set-point. In order to return the compartment temperature to this point, prior art systems operate at maximum capacity regardless of the degree of the deviation.
Once the desired compartment temperature is achieved, an additional problem arises. The temperature with the compartment begins to stratify, or separate. Warmer air rises to the top of the compartment and, likewise, cooler air settles to the bottom. This can result in substantial harm to food products stored within the appliance. The magnitude of the stratifications has historically been dependent on the location of a thermostat. Prior art systems typically measure the temperature of the compartment at a single measuring point, hence, not until the temperature at that location falls below the set level of the thermostat, is the refrigeration system activated. Once activated, the compressor has to lower the temperature of the compartment until the same measuring point reaches the pre-set level.
One method devised to reduce this stratification problem concerns employing an adjustable damper in a passage between the first and second compartments. This arrangement enables cooler air to pass from the freezer compartment to an upper portion of the fresh food compartment. Unfortunately, the addition of a damper alone simply does not solve the various problems of these known arrangements. To this end, it has also been proposed to incorporate a fan within a housing adjacent to the evaporator to assure a desired cooling air flow to the fresh food compartment. Accordingly, if the temperature of the fresh food compartment rises above the set-point, the damper is operated to allow the passage of forced cooling air from across the evaporator to the fresh food compartment.
Regard less of these known arrangements, there still lacks an efficient control arrangement that avoids both stratification in the fresh food compartment and rather large temperature variations prior to activation of the refrigeration system. Therefore, once, a desired operation temperature has been selected, the refrigeration system strives to maintain a uniform compartment temperature. However, without adequate air circulation within the compartment, the temperature will begin to stratify such that air located in the upper regions of the compartment will be substantially warmer than air in the lower regions. In addition, there is as inherent time delay in adjusting the compartment temperature which further promotes compartment stratification. Accordingly, there exists a need for a temperature control system adapted to maintain a uniform temperature throughout a refrigerated compartment, wherein the system responds rapidly to any temperature fluctuations and presents an improved air flow system designed to avoid thermal stratification.
The present invention is directed to a refrigerator which is energy efficient, has a reduced noise output, and exhibits minimal thermal stratification. In accordance with the invention, cooling air is drawn from a first or freezer compartment into an intake duct and delivered to a manifold located in a second or fresh food compartment of the refrigerator. A multi-position damper is arranged in the intake duct for regulating the flow of the cooling air. The manifold also preferably receives a flow of recirculating air through additional ducting exposed at varying height portions in the fresh food compartment. A stirring fan is arranged in fluid communication with the manifold to disperse the combined air flow through the fresh food compartment. Most preferably, the stirring fan is continuously operated.
In order to establish effective temperature regulation, the refrigerator includes a control system which is responsive to an arrangement for sensing an average temperature in the fresh food compartment. In accordance with the most preferred embodiment of the invention, the fresh food compartment is provided with an elongated metal shelf rail which extends vertically from an upper portion to a lower portion of the fresh food compartment. With this configuration, the shelf rail will reflect an average fresh food compartment temperature which is sensed by a temperature sensor provided on the shelf rail.
With this overall system, the temperature in the fresh food compartment can be effectively and efficiently maintained at a desired operating temperature, while essentially avoiding thermal stratification in the compartment. In any event, additional objects, features and advantages of the invention will become more readily apparent from the following detailed description of a preferred embodiment of the invention, when taken in conjunction with the drawings wherein like reference numerals refer to corresponding parts in the several views.